P550 Non-Mag Drill Collar

Chemical Composition
P550 is a special non-mag, austenitic Mn-Cr-N-steel with a high nitrogen content

C Mn Cr Mo N
max. 0.06 20.50-21.60 18.30-20.00 min. 0.50 min. 0.60

Mechanical Properties

Following mechanical properties are achieved by a special cold-working process over the
full length of the collar:

Yield Strength (min.) OD up to 6 7/8“ 140 ksi 965 N/mm²
0.2%-offset method  OD = 7" and larger 130 ksi 900 N/mm²
Tensile Strength (min.) 150 ksi 1035 N/mm²
Elongation (min.) 20 % 20 %
Reduction of Area (min.) 50 % 50 %
Impact Energy (min.) 60 ft.lb 82 J
Endurance Strength/N=105 (min): 80 ksi 550 N/mm2
Hardness Brinell (min.) 350 - 430 HB 350 - 430 HB

Magnetic Properties
Relative permeability: < 1,005

Corrosion Resistance

  • Transgranular SCC: Prevented by special surface treatments ( "PLUS" treatment, roller burnishing, shot peening).
  • Intergranular SCC: The occurrence of material sensitization is prevented by quenching after warm-forging. Each collar is tested acc. to ASTM A 262, Pract. A and E, last edition.
  • Pitting Corrosion: Due to a high chromium and nitrogen content a high resistance to pitting corrosion is given.

Non-Destructive testing

  • Magnetic inspection:
    Drill collars are 100% tested by a proprietary probe-testing process (“Hot Spot“-test).
    Magnetic permeability of each collar is certified with the printout of probe-testing.
  • Ultrasonic inspection:
    Each collar is ultrasonically inspected acc. to ASTM E 114, last edition as a minimum level.


P550 Non-Mag Drill Collars meet all requirements of API Spec. 7, last edition. All tests are carried out acc. to ASTM-Standards, last editions.

Prepared / released: H. Aigner Date: Oct 12, 2004